1. Field of the Invention
Aspects of the present invention relate to a blocking effect removal system and method, and more particularly, to a blocking effect removal system and method which extracts a homogeneous pixel segment, filters the extracted pixel segment according to a direction vector, and thereby can remove a blocking effect.
2. Description of the Related Art
Encoding of image data is critical to transmit an image or to store in a storage medium via a network having a fixed bandwidth. Much research has been conducted to efficiently transmit and store an image. A transform-based encoding method is most widely used, and more particularly, a discrete cosine transform (DCT) technology is widely used.
Codecs based on a local DCT such as Moving Picture Experts Group (MPEG), joint photographic experts group (JPEG), and H.264, use a local correlation of image. That is, such codecs divide an image into a plurality of blocks including N*N pixels, and individually apply a DCT for each block. In this instance, since a DCT is applied for each block, a connection among adjacent blocks is disconnected, and a discontinued frequency is shown on a block boundary.
Then, when an image is processed by a DCT-based codec, it can be visually evident that an image is divided into blocks by boundaries. The boundaries are referred to as a blocking artifact, and a blocking effect indicates an effect in which a blocking artifact occurs.
MPEG2 is a standard of digital broadcasting, and mobile devices such as DMB use a block DCT-based codec such as H.264 as a standard of moving picture. Accordingly, a deblocking technology is needed to be developed.
A blocking effect can be solved by using a filter such as a low pass filter (LPF) and applying a smoothing to a block boundary. However, it is needed that a high-frequency element such as an edge, included in an original image, is not corrupted when the smoothing is applied to a block boundary.
In a conventional art, a method of controlling a filtering strength for each block exists. In the method, adjacent blocks based on a block boundary are divided into a smooth pair and a detailed pair. Also, a method of controlling a filtering strength for each pixel exists. In the method, an edge map of an image is made for each pixel. In a filtering method, a method in which an overlapped DCT is performed and a high frequency due to blocking is selectively removed, has been used.
However, it is disadvantageous that above-described methods in a conventional art are unsuitable for a low complexity method easily applicable to a mobile terminal. Particularly, in a mobile broadcasting such as DMB, an image is compressed depending on a relative bit rate due to a limit of transmission line, and thus a blocking artifact is easily generated.
Thus, a method which is applicable to a variety of apparatuses and minimizes complexity of operations and a memory use is needed.